Heavy metal contamination is common throughout all vegetation. These heavy metals originate from soil and fertilizers, and are absorbed by plants. Cannabis is no exception to this contamination. These heavy metals possess different levels of acute and chronic toxicity, and need to be regulated. Heavy metals are only acceptable in trace amounts (usually measured in parts per million, or ppm). Standards and acceptable levels of heavy metals differ between jurisdictions. Check with your regional regulations to find out about the details of regulated heavy metals and their acceptable limits.